Persistent and relapsing infections associated with small-colony variants of Staphylococcus aureus

Clin Infect Dis. 1995 Jan;20(1):95-102. doi: 10.1093/clinids/20.1.95.


Small-colony variants (SCVs) of Staphylococcus aureus were cultured from five patients with persistent and relapsing infections. All five SCV strains were nonhemolytic and nonpigmented and grew very slowly on routine culture media in an ambient atmosphere. In several instances, these phenotypic characteristics led to the initial misidentification of the organisms in the clinical microbiology laboratory. All four strains available for further analysis were shown to be auxotrophs that reverted to normal growth and morphology in the presence of menadione, hemin, and/or a CO2 supplement. Similarly, these isolates were resistant to aminoglycosides under routine conditions but susceptible in the presence of the metabolic supplements. For two patients, the large and small colony forms isolated concurrently were indistinguishable when analyzed by pulsed field gel electrophoresis and thus represented phenotypic variants within individual clones. We propose a model relating the phenotypic characteristics of S. aureus SCVs with the clinical pattern of persistent and relapsing infection.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aged
  • Arthritis, Infectious / microbiology
  • Chronic Disease
  • DNA, Bacterial / genetics
  • DNA, Bacterial / isolation & purification
  • Female
  • Genetic Variation
  • Hemin / biosynthesis
  • Humans
  • Male
  • Middle Aged
  • Models, Biological
  • Osteomyelitis / microbiology
  • Phenotype
  • Recurrence
  • Sinusitis / microbiology
  • Staphylococcal Infections / microbiology*
  • Staphylococcus aureus / genetics
  • Staphylococcus aureus / growth & development
  • Staphylococcus aureus / pathogenicity*
  • Vitamin K / biosynthesis


  • DNA, Bacterial
  • Vitamin K
  • Hemin